Unlike direct heating with gas or heating elements, electromagnetic cookers indirectly heat a target object by virtue of electromagnetic induction. In an electromagnetic cooker, temperature will not increase except for at the target object, reducing risks of a burn and a fire. Further the emission of carbon dioxide is reduced. These characteristics appear to make electromagnetic cookers more popular.
For a material of a pan and the like used with an electromagnetic cooker, a thin stainless steel-clad steel plate including a stainless steel mating material and a low-carbon steel base material, and a clad steel plate having a stainless steel mating material and a base material made of aluminum or an aluminum alloy are often used in view of corrosion resistance and induction heating properties.
An electromagnetic cooker represents a safe and clean heating means as described above, but suffers from a slower heating rate and longer cooking time as compared with gas heating due to a limited power of the device as well as difficult broth penetration into food materials. Accordingly, a cookware product has recently been proposed including a stainless steel-clad steel plate having improved induction heating properties.
Meanwhile, a clad steel plate is known to have a use other than cookware. For example, Patent Document 1 proposes a two-layer or three-layer clad steel plate including a base material made of a mild steel having a carbon content of 0.005% or less and a mating material(s) made of stainless steel or nickel or a nickel alloy, the ratio (Al/N) of the amount of aluminum to the amount of nitrogen in the base material being 6 or more, and the amount of nitrogen contained in the mating material(s) being 0.01% or less.
Patent Document 2 proposes a stainless steel-clad steel plate having an outer layer material of stainless steel and a base material of low-carbon steel, the content of acid-soluble Al in the base material being 0.10 to 1.5% by weight.
Patent Document 3 proposes a clad steel material including an upper material, an intermediate material, and a lower material, the upper material including a ferrite-based stainless steel containing 10.0 to 30.0% by weight of Cr and having a plate thickness of 0.3 to 3.0 mm, the intermediate material including aluminum with a purity of 99% or more and having a plate thickness of 1.0 to 10.0 mm, and the lower material including a steel plate with a plate thickness of 3.0 to 30.0 mm.
Patent Document 4 proposes a method of manufacturing a patterned metal plate or a rainbow-colored metal plate, the method including cold-rolling or skin pass-rolling a clad material with a rolling roll having a pattern on a surface thereof, the clad material having a thin coating of a metal on a surface of an internal base material, the metal being softer than the base material.
Further, Patent Document 5 proposes a metal plate for a cookware product and a method of manufacturing the same, the metal plate having a large number of independent protrusions formed on a surface of the metal plate corresponding to an inner surface of the cookware product, and a flat continuous groove portion being formed between the respective independent protrusions.
Patent Document 1: Japanese Examined Patent Application Publication No. H05-14610
Patent Document 2: Japanese Unexamined Patent Application, Publication No. H11-77888
Patent Document 3: Japanese Unexamined Patent Application, Publication No. S64-40188
Patent Document 4: Japanese Unexamined Patent Application, Publication No. H02-263501
Patent Document 5: Japanese Unexamined Patent Application, Publication No. 2002-65469